4$ Human Knowledge very imperfeB, 
are fo extremely different, that every con- 
fiderate Obferver mu ft judge them owing 
to fome very different Property in Nature.— 
I have ventured to mention Attraction 
and Repulfion, as two Principles that we 
may fuppofe concerned in producing thefe 
different Appearances, but am very far from 
being obftinate in this Opinion, or un¬ 
willing to recede from it, whenever any 
more probable Caufe can be affigned. I 
am fufEciently fenfible how liable we are 
to be miftaken, and how very little we 
know even of the moft common Things. 
The very Elements that are continually 
about us, the Fire, the Water, the Air we 
breathe, and the Earth we tread upon, have 
many Properties beyond our Senfes to reach, 
or our Underftanding to comprehend : and 
when we imagine we know any one Thing 
perfectly, I am afraid we flatter and de¬ 
ceive ourfelves very grofly. It is our Hap- 
pinefs, however, and our Duty, to beftow 
lome Time and Pains in making ourfelves 
acquainted with the Productions and Changes 
that Providence continually brings about 
in a regular and conftant Manner. We 
are able to fee EffeCts, though their Caufes 
are beyond our Knowledge: but as no 
EffeCt can be produced without fome Caufe, 
when we behold Order, Harmony, and 
Beauty arife out of Confufion, by means 
of certain aCtive and unalterable Properties, 
where- 
